JPS63286524A - Production of shadow mask - Google Patents

Abstract

PURPOSE:To produce a shadow mask having an excellent perforating property by etching by subjecting a cold rolled steel sheet consisting of specifically composed C, Mn, S, Al, N, and Fe to perforation of many holes then to annealing in an atmosphere under specific conditions. CONSTITUTION:The cold rolled steel sheet consisting of <=0.004wt.% C, 0.05-0.50% Mn, <=0.010% S, 0.010-0.080% Sol Al, <=0.0100% N, and the balance Fe and inevitable impurities is subjected to perforation of many holes. This steel sheet is then annealed in gas contg. hydrogen and nitrogen. The annealing is executed at this time under the conditions satisfying either or both of maintenance of <=750 deg.C holding temp. of annealing and <=0 deg.C dew point of the annealing atmosphere. The shadow mask which has the excellent perforating property by punching, obviates generation of unevenness even after press molding and is used for a color television, etc., is thereby obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for producing a shadow mask for use in color televisions, color displays, etc., which has excellent etching perforation properties and does not cause unevenness even after press molding.

<Background of the Invention> Shadow masks are used as color selection electrodes in cathode ray tubes such as color televisions and color displays.

The manufacturing process of the shadow mask is generally as follows. First, a shadow mask material having a predetermined thickness is manufactured through processes such as melting the material, casting and rolling, and finally cold working. This shadow mask material is etched and perforated to form a flat mask. Furthermore, this flat mask is annealed to give it press formability, and then the mask is formed into a spherical surface by pressing.

It is blackened and becomes a shadow mask. There is also a method in which annealing to impart press formability is performed immediately after final rolling, and this is called a pre-annealing method.

To explain in more detail, first of all, taking low carbon AQ killed steel as an example of a method for producing a shadow mask material, the steel is melted in a converter, then continuously cast or ingot cast, and then hot rolled (if necessary, after forging). The material is hot rolled) and cold rolled, decarburized by open coil annealing, and then final cold rolled to a predetermined thickness. Thereafter, the cold rolled material is slit to obtain a shadow mask material having a predetermined width.

After degreasing the shadow mask material obtained in this way, photoresist is applied to both sides, a pattern is baked and developed, and holes are etched with an etching solution mainly containing ferric chloride. Cut it to make a flat mask.

Flat masks are usually annealed in a non-oxidizing atmosphere to give them press formability (in pre-annealing, this annealing is performed on the final cold-rolled material before etching), and after leveling, the mask is formed by pressing. Molded into a spherical shape.

Finally, the spherical mask is degreased and then subjected to a blackening treatment in a steam or combustion gas atmosphere to form a black oxide film on the surface, thus producing a shadow mask.

<Prior Art and Problems> A low carbon rimmed cold-rolled steel plate was used as the initial shadow mask material manufactured as described above. In this case, non-metallic inclusions or carbides in the steel may cause defective hole shapes during photoetching, and if low-temperature annealing is performed to prevent adhesion between the flat masks in the final annealing, the crystal grains of the steel will become smaller, resulting in press forming. Even if a leveler is applied beforehand, sufficient strain is not introduced, and there are drawbacks such as stretcher strain is likely to occur due to elongation at yield point due to solute C and solute N during press molding. This stretcher strain distorts the hole edges and causes color unevenness, so its occurrence must be prevented in order to satisfy the performance of the shadow mask.

In addition, when rimmed steel is annealed at high temperatures, the crystal grains become coarse and the edges of the pores are distorted when pressing the shadow mask. had to be severely restricted.

In order to improve these drawbacks, low carbon AQ killed cold rolled steel sheets with a C content of 0.005% or less, as shown in the above example, have recently been used.

However, in recent years, the definition of shadow masks has rapidly increased, and it has become necessary to drill many holes with high precision in cold-rolled steel sheets with a thickness of about 0.1 mm. In addition, as another move to improve color cathode ray tubes,
So-called FS tubes, which have a rectangular and flattened cathode ray tube front screen panel, are on the rise. By making the front square and flat, this design aims to increase the amount of information and reproduce images more faithfully, and also to reduce eye fatigue caused by the reflection of external light on the viewer. The shadow mask used for this FS tube has a plate thickness of 0.2 to 0.3111 in order to suppress the occurrence of color shift due to the doming phenomenon caused by thermal expansion.
A cold-rolled steel plate of approximately 100 mm is used.

As the definition of shadow masks increases and the number of FS tubes increases, it is no longer completely satisfactory even when using low carbon AQ killed cold rolled steel sheets, which had no problems in the past. .

The manufacturing process of the shadow mask after final cold rolling.

Mainly, after degreasing a cold-rolled steel sheet, a resist layer is applied, a pattern is baked, and after development, etching holes are made with a solution mainly containing ferric chloride to create a flat mask, and after this etching hole is annealed, the flat mask is formed into a predetermined shape. It consists of a step of press-forming into the shape of a shadow mask, and a step of forming a black oxide film on the surface of the shadow mask by heat treatment.In the etching and perforation step, segregated substances mainly composed of MnS due to central segregation are removed. Since the corrosion occurs more preferentially than the base portion, hole-like defects occur on the etched wall surface in that portion, causing a problem of so-called uneven transmission. This is due to the fact that the area traditionally used for hole-etching has increased dramatically as shadow masks have become more precise in recent years, and even if materials used are of a level that was previously thought to have no problems, they are now becoming defective. This is because the probability of this happening has increased.

In addition, even in cases where uneven penetration did not occur during the etching and perforation process, uneven penetration occurred after press forming during the step of annealing the flat mask in the first step and press forming it into a predetermined shape.

When we investigated this in detail, we found that M
There are segregated substances due to center segregation, mainly composed of nS, and the elongation characteristics of the area with this center segregation and the clean area with no center segregation are slightly different. It was discovered that this caused distortion, which caused uneven transmission. This phenomenon also occurs in recent years.
This is a problem that is increasing with the increase in the number of S tubes, and is truly a problem that has never existed before.

In view of this situation, the present inventors have developed a low carbon AQ for shadow masks that is mainly composed of MnS and aims to reduce segregation.
Although a significant improvement in etching perforability was confirmed by the development of killed steel, on the other hand, the shadow mask material S
When the content is reduced, the amount of nitrogen absorbed increases during normal annealing, resulting in a problem that unevenness occurs during subsequent press forming.

That is, in the annealing process during the production of shadow masks, a gas consisting basically of hydrogen and nitrogen has been used, and in order to prevent stretcher strain caused by solid solution C, a gas of 650~
Decarburization annealing was performed at a temperature of 850°C. However, with low S content, nitrogen absorption occurs under these conditions,
A problem arose in that local elongation unevenness occurred during pressing.

<Structure of the Invention> The present inventors have repeatedly conducted various studies regarding the above-mentioned problems, and have arrived at the present invention. 0.
50%, S 0.010% or less.

S o Q, AQ 0.010-0.080%, N0.
After drilling a large number of holes in a cold-rolled steel sheet consisting of 0.0100% or less, the balance being Fe and unavoidable impurities, annealing is performed in a gas containing hydrogen and nitrogen. Either setting the dew point to 0℃ or higher,
Alternatively, the method for producing a shadow mask is characterized in that annealing is performed under conditions that satisfy both conditions.

<Detailed Description of the Invention> Next, in order to explain the present invention more specifically, the reasons for limiting the components of the cold rolled steel sheet and the manufacturing conditions will be explained.

C: When the amount of C in a cold rolled steel sheet is large, iron carbides are generated, and these carbides impair etching perforability.

Furthermore, when a flat mask is annealed after perforation as a shadow mask, non-uniform molding (occurrence of stretcher strain) will occur during press molding unless the solid solution C is reduced.

In order to satisfy both of these requirements, it is necessary to set the upper limit of the C content of the cold-rolled aluminum killed steel sheet to 0.004%. C
If the content is within this range, the amount of solid solute C will be sufficiently small and there will be no problem. In order to efficiently reduce the C content to this level in a decarburization annealing furnace, it is desirable to reduce the C content to 0.060% or less at the steel manufacturing stage.

From the above, the C content of the cold-rolled steel sheet is 0.004% or less, and the C content before the hot-rolled steel sheet is 0.060% or less.

Mn: In addition to the purpose of deoxidizing, Mn is useful for improving the strength of steel without degrading the properties of the shadow mask.

In addition, the role of Mn is to combine with S in the steel to prevent red heat embrittlement of the steel. Therefore, Mn is at least 0.
05% is necessary, and it is desirable that the weight ratio of Mn and S is M n (%)/S (%)≧7.

However, when Mn exceeds 0.50%, it becomes too hard as a shadow mask and impairs the formability of a flat mask. Therefore, the component range of Mn is 0.05 to 0.50% S:
Reducing S in WI directly leads to reducing center segregation of MnS. When focusing on the center segregation of MnS, which is a problem in etching holes and press forming, the effect appears at 0.010% or less.

Furthermore, when forming ingots by continuous casting, further improvement is observed when electromagnetic stirring is used.

SoQ, AQ: In addition to deoxidizing the steel and reducing inclusions, SoQ, AQ fixes solid solution N as ARN and prevents stretcher strain during press forming.
AQ must be contained as (acid-soluble AQ). However, when it is contained in a large amount, it deteriorates ductility.

From the viewpoint of deoxidation, 0.010% or more is required, and from the viewpoint of ductility, the upper limit is 0.080%.

In addition, in order to fix solid solution N as Alx (SoQ
, A'fi that satisfies AQ%-0,003)/N%≧6
It is desirable to add a certain amount.

N: Since N increases the elongation at yield point and causes stretcher strain, it is preferable that it be as small as possible. However, if it is reduced excessively, it will be costly, so in this patent, it is set to 0.0100% or less.

Regarding the behavior of nitrogen absorption during annealing, as shown in FIGS. 1 and 2, when the holding temperature is higher than 750°C and the dew point of the atmosphere is lower than 0°C, nitrogen absorption tends to increase. This tendency is not remarkable when the S content is higher than 0.010%, and as shown in Figure 3, the S content is higher than 0.010%.
% or less shows significant nitrogen absorption.

Note that although the annealing atmosphere gas basically consists of hydrogen and nitrogen gas, it is assumed that it naturally contains trace gases such as oxygen that are inevitably mixed in.

<Example> A large number of holes were drilled in a cold-rolled steel plate having the composition shown in Table 1,
The situation of etching and perforation unevenness was checked and is also listed in Table 1. This material was annealed under the conditions shown in Table 2, and the occurrence of unevenness after pressing was investigated. The results are also listed in Table 2.

As is clear from Table 1, Examples A to C of the present invention have no unevenness after etching and have extremely good etching perforation. On the other hand, in Comparative Examples DE, streak-like transmission unevenness parallel to the rolling direction occurred.

Table 2 shows the situation when pressing was performed after annealing, and Examples 1 to 5 of the present invention used masks A and B in Table 1, and there was no uneven elongation during pressing, which was extremely good. It was possible to obtain a shadow mask. On the other hand, Nα of comparative example ■
Samples Nos. 6 to 9 used the masks A and B in Table 1, but because the holding temperature was high and the dew point was low, uneven elongation caused by nitrogen absorption occurred.

In addition, NQIO~12 of Comparative Example (■) uses the mask shown in the first table, and the nitrogen absorption is slight under all conditions, but there are transmission lines in the direction parallel to the rolling direction that are thought to be caused by segregation of MnS. has newly occurred.

Margins below Table 1 Table 2 Other annealing conditions 8%--ba12. N2 hold 15min

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between annealing holding temperature and nitrogen absorption amount for two steels with different S contents (8% H2 - residual N2
, dew point -30℃, held for 30 minutes), Figure 2 is a graph showing the relationship between dew point and nitrogen absorption amount (8% H2 - residual N2.800℃).
, held for 30 minutes), Figure 3 is a graph showing the relationship between S content and nitrogen absorption (8% H2 - residual N2, dew point -30°C, 80%
0°C x 30 minutes). 1st cause ('C) Fig. 2 Demand bear (oC) Fig. 3 3 combined amount (%) Procedural amendment dated August 6, 1988, Patent officer Kunio Koyo case Indication Patent Application No. 120193 of 1988 Title of Invention Person who corrects the manufacturing method of shadow mask

Claims (1)

[Claims] (1) C0.004% or less, Mn 0.05-0 in weight%
．． 50%, S0.010% or less, Sol. Al0.01
After drilling a large number of holes in a cold rolled steel sheet consisting of 0 to 0.080%, N 0.0100% or less, the balance Fe and unavoidable impurities, when annealing in a gas containing hydrogen and nitrogen,
The annealing holding temperature is 750℃ or less, and the dew point of the annealing atmosphere is 0℃.
A method for manufacturing a shadow mask, characterized in that annealing is performed under conditions that satisfy one or both of the above conditions.